EP983 - The Optimum Mesh Shape for Ventral Mesh Rectopexy: A Finite Element Analysis

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Purpose/Background: Colorectal surgeons still cannot agree on the optimal shape for mesh used in Ventral Mesh Rectopexy (VMR). Rectangular, L-shape, and trapezoid shape are used based on individual surgeon preference. Synthetic and biologic meshes each present unique mechanical properties that impact their performance in surgical settings. This study employs finite element analysis (FEA) to evaluate the structural responses of these mesh shapes under physiologic forces to identify the best shape.

Methods/Interventions: FEA using Ansys software simulated the performance of three biologic mesh geometries (L-shape, rectangular, and trapezoidal) under physiologic conditions mimicking ventral rectopexy. Key metrics, including total deformation, force reaction, safety factor, equivalent elastic strain, and von Mises stress, were assessed to evaluate each mesh’s load-bearing capacity and identify potential failure points.

Results/Outcomes: FEA revealed significant performance differences across the three configurations, each demonstrating unique strengths and limitations. The trapezoidal mesh exhibited the least deformation (0.0098 m), indicating an effective balance between flexibility and support, which suggests suitability for anatomical conformity and stability in ventral rectopexy. The rectangular mesh, with moderate deformation (0.1446 m), provided high structural stability, as reflected by its safety factor—the highest among designs—with an average of 3.5 and a minimum of 0.42 at its weakest points, reinforcing its capacity to withstand substantial load without compromising integrity.
The L-shaped mesh displayed the highest deformation (0.0143 m) and the lowest safety factor, with an average of 1.5 and a minimum of 0.1579, indicating potential instability under high-stress conditions. Von Mises stress analysis confirmed these findings, showing that both rectangular and trapezoidal meshes effectively distributed load with peak stresses of 9.4 MPa and 8.5 MPa, respectively. In contrast, the L-shaped mesh recorded a higher von Mises stress (19 MPa), highlighting vulnerability to stress concentration and potential for structural failure.
Collectively, these results indicate that the trapezoidal mesh’s balance of flexibility and support makes it a promising candidate for ventral rectopexy, with the rectangular mesh as a viable alternative where rigidity is essential. The L-shaped mesh appears less suited to high-stress applications, though stress-reduction strategies, such as corner rounding, enhanced durability across all configurations.

Conclusion/Discussion: The findings suggest that trapezoidal is the most reliable shape for ventral mesh rectopexy. The trapezoidal mesh balances flexibility and durability, adapting anatomically while maintaining support. This study guides mesh selection for ventral rectopexy by aligning structural properties with surgical demands, promoting configurations that optimize outcomes.